We haven't paid "the Apple Tax" ... as a developer you have to pay Apple in order to sign your packages. We are an "unknown" developer to them, and the package is unsigned. This DOES NOT mean the package cannot be verified. This is exactly why we provide hash sums to verify your downloaded package.

The Team is discussing possible solutions, but for now, the command above is you saying "yes, I know I downloaded this, and verified I know the developers" manually.

This will work after the "release" or "autobuild" updates; it will not produce sound if run without the update, i.e., straight from the initial Zip file. When it does launch, it sends torturous stuff to the speakers for a few seconds before it settles.

I appreciate any assistance and recommendations with regards to this problem. Thank you for your help and time.

Or you can do this to solve this issue which I read somewhere, it worked for me:
"Move Xonotic.app somewhere else and back [again] using the Finder."
e.g. drag Xonotic.app to your desktop, then drag it back to it's original place again. Presto, it works.

Somebody on IRC said it's possible to CTRL+click and choose Open from the menu, can somebody on a Mac test this? Does it also persist like moving the .app somewhere else and back so it's possible to open xon normally after that? https://support.apple.com/kb/PH25088?locale=en_US